A conventional scroll-type compressor disclosed in Japanese Unexamined Utility Model Publication No. 58-8783 is illustrated in FIGS. 10 and 11. This scroll-type compressor includes a fixed scroll 102 having a spiral element 101 integrated with an end plate 100, and a movable scroll 105 having a spiral element 104 integrated with an end plate 103. The fixed scroll 102 and movable scroll 105 engage with each other at the spiral elements 101 and 104.
As the movable scroll 105 revolves around its own axis at a given radius, pockets 106 to 109 between both spiral elements 101 and 104 are shifted toward the spiral centers of the spiral elements 101 and 104 while reducing their volumes. This movement causes the refrigerant gases in the pockets 106-109 to be compressed.
Grooves 110 and 111 are formed in the end faces of the spiral elements 101 and 104 of the fixed and movable scrolls 102 and 105. Seals 112 and 113 are fitted in both grooves 110 and 111 to secure the sealing with the end plate 100, 103 of the mating scroll 102, 105. The grooves 110 and ill are formed about the spiral centers of the spiral elements 101 and 104 in a range of nearly 540 degrees. Therefore, the seals 112 and 113 have lengths matching with the range of 540 degrees about the spiral centers of the spiral elements 101 and 104, and are not present outside the range.
The reason is as follows. The gas pressures in the pockets 108 and 109 located close to the centers of both scrolls 102 and 105 are high, and the gas pressures in the pockets 106 and 107 on the peripheral sides do not become so high. Therefore, it is unnecessary to improve the sealing performance on the peripheral sides of the spiral elements 101 and 104, eliminating the need for the seals 112 and 113.
As mentioned above, since the gas pressures in the pockets 106 and 107 on the peripheral sides do not become high, it is desirable that the peripheral portions of the spiral elements 101 and 104 be thinner in order to make the compressor lighter. When the peripheral portions of the spiral elements 101 and 104 are made thin, the seals 112 and 113 cannot be provided at those thin portions. Further, if the grooves 110 and 111 and the seals 112 and 113 are short, processing of the grooves 110 and 111 becomes easier and a less amount of materials be needed for the seals 112 and 113, thus reducing the manufacturing cost.
Generally speaking, a scroll type compressor has a dimensional tolerance between the fixed scroll and movable scroll. In other words, there is a clearance in the axial direction between both scrolls.
At the time the movable scroll 105 revolves, the movable scroll 105 may slightly tilt as shown in FIG. 11, for example, due to variations in various forces acting on the movable scroll 105. This inclination of the movable scroll 105 causes the corner portions of the peripheral end faces of the spiral elements 101, 104 of the fixed and movable scrolls 102, 105 where the seals 112, 113 are not present to contact the end plates 100, 103 of the matching scrolls 102, 105. This contact may cause power loss, vibration or noise, or may damage the end faces of the spiral elements 101, 104 and the end plates 100, 103 when driving the compressor.
To prevent the end plates 100, 103 from being damaged, a process has been adopted for adhering thin steel plates to the inner surfaces of the end plates 100, 103. This of course increases the number of parts. What is more, while damage to the end plates 100, 103 can be prevented, it is not possible to prevent vibration and noise or prevent damages to the spiral elements 101, 104.